I need a head swap for my WD 4TB HDD. Can u plz tell me what each character of a western digital DCM code [eg: HHNNHT2CAB] represent and which characters should match for a Head Swap!!! If the entire model number is same, willl this DCM code HHNNNT2MHB a match for HHNNHT2CAB?

The letters “T2” is what needs to match in the DCM code for the heads to be a match. That along with the center part of the code after the dash in the model number (e.g. WD40EZRZ-00WN9B0) to be sure the drives are the same family.

However, don’t expect it’s just an easy swap and the drive is going to work. If you don’t have a proper clean room your chance of success is virtually zero. And, if you did have a proper clean room, I doubt you’d be asking such a question here.

Even if you managed to somehow replace the heads without contaminating the drive or damaging them, you’d still likely need to make modifications to the drives firmware code to stabilize it enough to read any data.